This invention relates to a suspension control system for use with an automotive vehicle supported on front and rear pairs of road wheels to control the damping force characteristic of each of the shock absorbers interposed between a sprung mass (vehicle body) and an unsprung mass (corresponding one of the road wheels).
For example, Japanese Patent Kokai No. 61-163011 discloses an automotive vehicle suspension control system for controlling the damping force characteristics of the shock absorbers provided on an automotive vehicle. The conventional suspension control system is arranged to suppress vibrations on the vehicle body by controlling the shock absorber damping force characteristics toward the hard side when both of the sprung mass vertical velocity and the relative velocity between the sprung and unsprung masses have the same sign and to suppress the unsprung mass input to be transmitted to the sprung mass by controlling the shock absorber damping force characteristics toward the soft side when the sprung mass vertical velocity and the relative velocity between the sprung and unsprung masses have different signs. The sprung mass vertical velocity is calculated based on the sprung mass vertical acceleration sensed with the use of a vertical acceleration sensor mounted on the sprung mass (vehicle body). Since the vertical acceleration sensor is fixed to detect the sprung mass vertical acceleration in a detection perpendicular to the road surface, however, the vertical acceleration indicative signal produced from the vertical acceleration sensor will includes a vehicle longitudinal acceleration component superimposed thereon to drift the vertical acceleration indicative signal when the vehicle is inclined into a scutting or diving position. This sensor signal drift causes introduction of errors into the shock absorber damping force characteristic control to degrade the vehicle driving stability.